The present invention relates to a high pressure sensor having a pressure port that is separate from the housing.
High pressure sensors have found utility in a number of different applications. For example, high pressure sensors are often employed in the area of automotive controls to obtain a measurement of certain pressure parameters such as engine oil pressure, transmission fluid pressure or brake pressure. High pressure applications generally utilize an integral stainless steel housing and pressure port which attaches to the pressure vessel by a threaded fitting, for example.
One of the problems of an integral housing made of high strength stainless steel is that these pressure sensors are very expensive and difficult to machine. For example, the pressure sensors may have housing installation sizes (hexagonal shape) that range from 24 mm-27 mm from flat to flat. However, the pressure ports of these pressure sensors may be in the 12 mm diameter range. Current technology achieves this reduction in size with an integrated single pressure port/housing part. To form the integrated pressure port/housing, the part is made from 24 to 27 mm hex stock that is machined down to 12 mm diameter in the port section. As mentioned above, the high strength stainless steel that the pressure sensors are made from is expensive and very difficult to machine. However, it is one of the few materials that is acceptable for the application due to the material strength required to deal with the stresses induced by system pressures reaching 3,000 bars, for example.
The machining from 24 mm to 27 mm hex down to a 12 mm diameter at the port involves a lot of machine time and tool wear. Furthermore, the machining creates a large amount of wasted scrap material, and hence, wastes expensive material.
There is a need for a high pressure sensor that reduces the cost of manufacture, but creates a mechanically sound high pressure sensor.
These and other needs are met by embodiments of the present invention which provide a pressure sensor comprising a pressure port having first and second ends and a fluid chamber extending through the pressure port with an opening at a pressure inlet at the second end of the pressure port and terminating at a diaphragm at the first end of the pressure port. The pressure sensor also comprises a housing having a central opening that surrounds the outer circumference of the pressure port along only a portion of the axial length of the pressure port. A retaining element is provided between the housing and pressure port and axially locks the pressure port relative to the housing. A fixative covers the retaining element to lock the retaining element in place. The pressure port has a first section with a non-circular outer circumference configured to mate with the inner circumference of a first section of the central opening of the housing to prevent relative rotation between the pressure port and the housing.
The earlier stated needs are also met by embodiments of the present invention which provide a high pressure sensor comprising a single-piece machined pressure port with a fluid chamber having a fluid inlet at a first end, and a housing surrounding a portion of the pressure port and mechanically coupled to the pressure port such that the pressure port is rotationally and axially locked with respect to the housing.
The provision of a pressure port and a housing surrounding a portion of the pressure port allows the pressure port and housing to be separately manufactured. In a high pressure sensor, exposed to pressures greater than 10,000 psi, a high-grade material is required for the pressure port. However, the present invention avoids the machining of a single-piece housing and integral pressure port from a relatively large-diameter hex stock. In other words, assuming that the housing is required to have a diameter between about 24 mm to 27 mm and the pressure port is required to have a diameter of approximately 12 mm, the prior art integral high pressure sensor is machined from 24 to 27 mm hex stock. The machining of the pressure port down to 12 mm diameter is difficult to achieve and creates a lot of expensive wasted scrap material. Furthermore, the extensive machining involves excessive machine time and tool wear. By contrast, with the present invention, only the smaller diameter pressure port is machined. This allows the pressure port to be machined from a smaller, less expensive 16 mm diameter cylinder, rather than an equivalent length of 24 to 27 mm hex stock. The amount of scrap material is greatly reduced. Furthermore, the present invention allows the housing of the pressure sensor to be manufactured from a less expensive material than that of the pressure port, and one that is also easier to machine.
The earlier stated needs are also met by embodiments of the present invention which provide a method of forming a high pressure sensor comprising the steps of forming a pressure port by machining the pressure port from high strength material stock. A separate housing is formed from a lower strength material, this housing having a central opening. The pressure port is inserted through the central opening of the housing with a first section of the pressure port remaining within the central opening and a second section of the pressure port extending externally from the central opening and the housing. The pressure port is then rotationally and axially locked to the housing.
The foregoing and other features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.